(From Acknowledgements)

ACKNOWLEDGMENTS

The author acknowledges and expresses thanks to ATK Launch Systems and NASA for

authorization to display internal flow in the Space Shuttle solid rocket motor nozzle in

Figure 2-16 (b) and nozzle vectoring data in Figure 2-17, and to technical artist Alan

Eaton for Figure 2-18 (property number A045477a, ATK Launch Systems, Inc., copyright

© 2005) showing the Space Shuttle roll maneuver with left and right solid rocket motor

labels added.

https://ntrs.nasa.gov/search.jsp?R=20090008515 2018-08-26T22:32:24+00:00Z

2.8.2 Space Shuttle Solid Rocket Motor Nozzle Internal Flow

Each Space Shuttle is boosted by two solid rocket motors (Figure 2-16a), which

are 126 feet long and 12 feet in diameter. Figure 2-16 (b) shows an enlarged upper

cross section of the nozzle. Combustion products entering the nozzle experience

maximum compression at the throat where the nozzle internal diameter is minimal. Aft

(to the right) of the throat, nozzle diameter increases. Gases exiting the throat expand,

increase in velocity, and generate thrust.

(a) (b)

Figure 2-16, Illustration of the Space Shuttle Booster, Nozzle, and Nozzle InternalCombustion Flow. (a) Space Shuttle solid rocket motor booster and section view ofnozzle. (b) Enlarged nozzle section, the red-green-blue-yellow (RGBY) color wheelindicates direction, and circular data image of internal combustion flow. Interestingfeatures include two counter-rotating vortices A and B, flow impingement on the nozzlesurface at C, and a narrow particle shear zone at D.

The flow direction shown in Figure 2-16 (b) was computed with FLUENT

computational fluid dynamics software (FLUENT 2008), for the Space Shuttle solid

rocket motor nozzle at 67 sec from ignition (Permission documentation given after the

Appendices). The dataset comprises 30,351 observations of five variables; node

identification, axial and radial coordinates in meters (m), and axial and radial velocity

components in m/sec). With direction of the flow aft (right) equal to yellow, upward equal

to red, forward (left) equal to green, and down equal to blue, the large counterclockwise

pattern in the cavity above the nozzle throat and centered at point A indicates a

counterclockwise flow. The smaller pattern at the right end of the cavity and centered at

point B indicates a clockwise flow. These two vortices mesh like oppositely rotating

gears. At point C, combustion products flowing down impact the nozzle outboard

surface and rapidly turn forward. Point 0 is a high shear zone where particle breakup

occurs. The circular data image easily shows much more structural information than a

vector plot, which is frequently used for these data, would be able to show. In particular,

a vector plot easily could miss the narrow high shear zone at Point D.

2.8.3 Space Shuttle Solid Rocket Motor Nozzle Vectoring Circular Time Series

Nozzle vector direction angle is the angle a nozzle points to in the plane

perpendicular to the motor axis. Figure 2-17 (a) shows the RGBY color wheel coding

direction. Figure 2-17 (b) (Permission documentation given after the Appendices) shows

the direction angle of a subset of nozzles for the time period from 5 sec to 23 sec after

ignition. The complete dataset comprises about 3,000 observations. Other variables

are orbital altitude in nautical miles (nm) and angle in degrees of the Space Shuttle

trajectory relative to the Earth equatorial plane. Each narrow horizontal band of colors

indicates a circular time series of direction angle with time increasing from left to right.

The observations (horizontal strips) were vertically sorted to show structures hidden by

alpha-numeric ordering of the observations and by variation. The horizontal strips are

sorted first by location of the nozzle (left side then right side of the motor), second by

angle of the Space Shuttle trajectory to the equatorial plane, and last by orbital altitude.

In Figure 2-17 (b), the prominent red horizontal band shows that the left side rocket

nozzle tends to vary about the O-degree location (red), and the overall blue horizontal

band above the red band shows that the right side rocket nozzle tends to vary about the

180-degree location (blue). Given the rotated assembly of the rocket motors, the red

and blue directions mean that the left and right nozzles tend to be pointed toward Earth.

The blue vertical band at about 10 sec shows the turning of the left side nozzle to

initiate the Space Shuttle roll maneuver as illustrated in Figure 2-18. The roll maneuver

orients the cargo bay towards the Earth to satisfy communication, scientific, and Space

Shuttle engineering requirements and provides the astronauts with a spectacular view of

Earth (Brown 2003). The nonrandom diagonal structures between about 14 sec and 23

sec, which were revealed by sorting the observations by inclination and orbital altitude,

show that nozzle vectoring following initiation of the roll maneuver is affected by

inclination and altitude.

Figure 2-17 (c) is an enlargement of one sequence of nozzle data in Figure 2-17

(b) near the tail of the arrow connecting Figures 2-17 (b) and (c).

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(a)

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5 10 15

(b)

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20 Time (sec)

6 8 10

(c)

12 14Time (Sec)

Figure 2-17, Time Series of the Space Shuttle Booster Nozzle Direction Angle. Directionangle is the direction the nozzle is pointing toward in a plane perpendicular to thebooster axis. (a) RGBY color wheel, (b) Circular time series families, and (c)Enlargement of one time series. The vertical and diagonal structures in (b) reflect rollmaneuver as influenced by inclination and altitude.

Left solidrocket motor

7 10 13 16 19

A045477a

©ATK Launch Systems

20 23Time (sec)

Figure 2-18, Illustration of the Space Shuttle Roll Maneuver Versus Time from Ignition.The time scale is nonlinear to show rotation in equal angular increments.